In hard disc drives, recording heads commonly write to a continuous magnetic layer on the surface of recording media. In these drives, the synchronization or timing of the recording head writing process relative to the rotation or position of the recording media has a relatively large margin of error. For example, if the writing process is a little early or a little late in its timing relative to the disc rotation, the information intended to be written may still be recoverable during the reading process. However, in hard disc drives or other storage devices with bit patterned media, synchronization of the writing process relative to the rotation or positioning of the recording media becomes less tolerant of errors.
In bit patterned media, the surfaces of the recording media have individual, discrete media dots made of magnetic materials. These media dots are surrounded by and separated from each other by nonmagnetic materials. In the case of writing to bit patterned media, the synchronization of the writing process relative to recording media becomes more critical. For example, if the writing process is too early or too late, the writer may not write to the intended media dot or even to any media dot at all. In this situation, the information that was intended to be written may not be recoverable during the reading process.